1. Field of the Invention
This invention is directed to power failure detection circuits, in general, and, more particularly, to circuits for detecting a power failure in a computer system and for preventing the system from operating in the absence of proper input power.
2. Prior Art
There are many circuits known in the art which serve the purpose of detecting power failure, insufficient power and the like. These circuits range anywhere from a simple relay circuit which merely drops out when the power applied to a circuit falls below a specified level to very complicated circuits for detecting power supply signals within very limited ranges.
Some of these circuits are arranged to permit the ultimate circuit or system to become operative again when the input power reaches a prescribed level. However, in many instances, this is not a significant problem inasmuch as the system merely becomes operative again and performs its specified function. However, in many instances, such as computer systems and the like, it is essential that the system not become operative again until the power supplied thereto reaches a specific level, for example, a level which renders the logic circuits in the computer operative.
Most of the circuitry which performs this function (i.e. power failure detection) is quite complex and, therefore, expensive. It is highly desirable to provide such a circuit which detects a power failure and prevents operation of the system until power reaches a prescribed level while doing so in an inexpensive and relatively simple manner.